This invention concerns press mounted cams, which are mechanisms installed in forming presses to produce a feature on the formed part, such as a punched or tapped hole. Where the feature must be formed by tool motion along a direction at a working angle transverse to the direction of press motion, such cams are used to produce this tool motion.
These cams are comprised of a “slide”, carrying the tool, a “body” or “adapter” affixed to one of the die parts or press platens on which the slide is slidably mounted and a separate “driver” mounted on the other of the die parts or press platen. The driver engages the slide and drives the same by mating cam surfaces when the press is operated.
In an “aerial” cam shown in FIG. 1, a slide 12 is suspended on a body of adapter 10 mounted to the upper platen 2 or die part 6. A driver 14 is mounted to the lower platen 4 or die part 8 and has a fixed inclined cam surfaces 16 extending parallel to the working angle, typically defined by wear plates affixed to faces on the driver 14 and slide 12.
As the upper platen 2 descends, a resulting cam action causes the slide 12 to be advanced along the working angle against the resistance of one or more springs 15 with tooling T projecting from the slide 12 in that direction. The horizontal component of the motion requires that the working slide 12 also move laterally on the adapter 10. Engaged horizontal bearing surfaces 18, 20 are provided on the top of the slide and the bottom of the adapter 10 for this reason. In other configurations, an angled surface may be on the adapter, and a horizontal surface on the driver as the embodiment seen in FIG. 10.
In a “die” or “base” mounted cam (shown in FIG. 2) the slide 12 and adapter 10 are both mounted to the lower platen 4 or die part 8 and do not move, but rather the drive 14 mounted to the upper platen 2 or die part 6 descends to engage the slide 12.
The die mounted cam thus does not result in vertical movement of the heavy slide when the press is operated which is necessary in an aerial cam, but which can cause problems as described below. However, aerial cams are often necessarily used to create a clearance space allowing transfer of the workpiece into and out of the die.
In a conventional aerial cam, a slide 12 (FIGS. 3 and 4) is suspended on a body or adapter 10 mounted to the upper platen. A driver 14 is mounted to the lower platen and has fixed inclined cam wear surfaces 16, 16A extending parallel to the working angle, typically defined by wear plates affixed to faces on the driver and slide.
As the upper platen descends, cam action causes the slide to be advanced along the working angle with tooling projecting from the slider in that direction. The horizontal component of the motion requires that the working slide 12 also move laterally on the adapter 10. Engaged bearing surfaces 18, 20 are provided on the top of the slide and the bottom of the adapter for this reason.
In order to accurately locate the tooling, the working slider must be accurately located laterally when engaging the driver and to achieve this, the practice has been to form the lower cam surfaces 16A in a V-shape so as to provide lateral location of the slide on the driver as well as a camming surface as the slide engages the driver.
Additional flat surfaces 16B are sometimes required for larger sized aerial cams to provide adequate area to distribute the stresses imposed by the press. Precision machining of the compound sloping V-shape camming surfaces is difficult and adds substantially to the cost of making the slider 12 and driver 14.
The slider 12 is suspended on the adapter 10 by means of side plates 20 engaged with plates hooked over plates 22 attached to the sides of the slider 12. The slider 12 is guided along the plates 20, 22 when being advanced by the camming action on the slider caused by the descent of the press upper platen.
The plates 22 are confined between side walls 24 to be laterally guided. A vertical hooked bar 26 is mounted on each side to reinforce the fixing of the plates 20.
Particularly in larger sizes, the need to machine the adapter 10 and slide 12 at locations on the outside of these components requires large size machining centers, adding to substantially to the cost of manufacturing the aerial cam.
Due to the large mass of the components, an auxiliary roller cam 28 is provided to initiate and assist slider motion by engagement with a machined slot 30 on the driver 14, just prior to engagement of the cam surfaces. This helps to initiate motion of the slider prior to engagement of the cam surfaces to reduce noise, shock and wear of the cam surfaces. However, this feature also adds substantially to the cost of such aerial cams.
A positive retraction auxiliary cam comprised of cam bars 32 and 34 is also provided to insure return movement of the slide 14 if return springs in pockets 36 should fail due to excessive shock loading.
A substantial practical difficulty encountered in manufacturing such cams is the great variety of configurations needed. Availability in a large number of working angles and lengths are required. Typically, the angle between the slide upper and lower surfaces is maintained constant, and the driver and adapter angles are varied with changes in the working angle.
The adapter, slide and driver have heretofore been machined from castings, a unique casting required for each of these components for each cam configuration, which is very costly particularly in the larger sizes.
It is an object of the present invention to provide a press mounted cam which eliminates hard to machine features, and is much easier to manufacture in the large number of configurations needed so as to substantially lower its cost of manufacture.